KNIGHT-SHIFT OF ADSORBED HYDROGEN ON RU-CU BIMETALLICS

The Friedel sum rule has been applied successfully to calculate and in terpret the experimental proton Knight shift resulting from hydrogen c hemisorbed on Ru-Cu bimetallic particles. Knight shifts have been calc ulated as a function of surface site occupancy for a very dilute conce ntration of Cu in Ru. With a full monolayer of Cu atoms on Ru the Knig ht shift, K, is found to be approximate to -7 ppm in contrast with the value K approximate to 94 ppm for hydrogen on pure Cu. The theoretica l results indicate that except for very large concentrations of Cu in Ru, when 2-dimensional Cu island formation takes place, the protons re sonate at frequencies closer to the frequency for the H/Ru system in q ualitative agreement with the experimental findings.